Two methods for analyzing fluorosis data based on Dean's classification system are presented and illustrated. The data are derived from examination of four groups of children, having 1, 2, 3 and 4 times optimal fluoride concentrations in their water systems. The first method, ridit analysis, is based on the rank ordering of the data, and provides an estimate of the probability that a randomly selected subject from one group has a more severe level of fluorosis than a randomly selected subject from another group. The second method used to compare groups is based on the number of fluorosed teeth of the subject. Each method identified the same three statistically distinguishable levels of fluorosis relative to fluoride concentration: the optimal group had the lowest level, the 2 and 3 times optimal groups a higher level, and the 4 times optimal group the highest level. The correlation found between Dean's Index and the number of fluorosed teeth for the same subject was 0.77.